On multi-modulation schemes to increase the rate of space-time block codes

In this paper, multi-modulation schemes (MMSs) are employed to increase the rate of our two new Complex Orthogonal Designs (CODs) proposed for eight transmit antennas, namely C₁ and C₂, corresponding to the Amicable Orthogonal Designs (AODs) (8;1,1,2,2;1,1,2,2) and (8;1,1,1,4;1,1,1,4), respectively. In addition, the optimal inter-symbol power allocation in the proposed codes in single modulation as well as in MMSs in Additive White Gaussian Noise (AWGN) channels is examined. It turns out that, in some modulation schemes, equal power transmission per each symbol time slot is not only optimal from the technical point of view, but also optimal in terms of achieving the best symbol error probability. The principles examining the MMSs in order to increase the rate of space-time block codes (STBCs) and the optimal power allocation for multi-modulated STBCs mentioned here can be generalized for STBCs of other orders without any difficulty.